content: /**
   * Copyright (c) 2016-present, RxJava Contributors.
   *
   * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
   * compliance with the License. You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software distributed under the License is
   * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
   * the License for the specific language governing permissions and limitations under the License.
   */
  
  package io.reactivex.interop.internal.operators;
  
  import org.reactivestreams.*;
  
  import hu.akarnokd.reactivestreams.extensions.RelaxedSubscriber;
  import io.reactivex.common.*;
  import io.reactivex.common.exceptions.Exceptions;
  import io.reactivex.common.functions.BiFunction;
  import io.reactivex.common.internal.functions.ObjectHelper;
  import io.reactivex.flowable.*;
  import io.reactivex.flowable.extensions.*;
  import io.reactivex.flowable.internal.operators.FlowableReduce;
  import io.reactivex.flowable.internal.subscriptions.SubscriptionHelper;
  import io.reactivex.observable.*;
  
  /**
   * Reduce a Flowable into a single value exposed as Single or signal NoSuchElementException.
   *
   * @param <T> the value type
   */
  public final class FlowableReduceMaybe<T>
  extends Maybe<T>
  implements HasUpstreamPublisher<T>, FuseToFlowable<T> {
  
      final Flowable<T> source;
  
      final BiFunction<T, T, T> reducer;
  
      public FlowableReduceMaybe(Flowable<T> source, BiFunction<T, T, T> reducer) {
          this.source = source;
          this.reducer = reducer;
      }
  
      @Override
      public Publisher<T> source() {
          return source;
      }
  
      @Override
      public Flowable<T> fuseToFlowable() {
          return RxJavaFlowablePlugins.onAssembly(new FlowableReduce<T>(source, reducer));
      }
  
      @Override
      protected void subscribeActual(MaybeObserver<? super T> observer) {
          source.subscribe(new ReduceSubscriber<T>(observer, reducer));
      }
  
      static final class ReduceSubscriber<T> implements RelaxedSubscriber<T>, Disposable {
          final MaybeObserver<? super T> actual;
  
          final BiFunction<T, T, T> reducer;
  
          T value;
  
          Subscription s;
  
          boolean done;
  
          ReduceSubscriber(MaybeObserver<? super T> actual, BiFunction<T, T, T> reducer) {
              this.actual = actual;
              this.reducer = reducer;
          }
  
          @Override
          public void dispose() {
              s.cancel();
              done = true;
          }
  
          @Override
          public boolean isDisposed() {
              return done;
          }
  
          @Override
          public void onSubscribe(Subscription s) {
              if (SubscriptionHelper.validate(this.s, s)) {
                  this.s = s;
  
                  actual.onSubscribe(this);
  
                  s.request(Long.MAX_VALUE);
              }
          }
  
          @Override
          public void onNext(T t) {
              if (done) {
                  return;
              }
              T v = value;
              if (v == null) {
                  value = t;
              } else {
                  try {
                      value = ObjectHelper.requireNonNull(reducer.apply(v, t), "The reducer returned a null value");
                  } catch (Throwable ex) {
                      Exceptions.throwIfFatal(ex);
                      s.cancel();
                      onError(ex);
                  }
              }
          }
  
          @Override
          public void onError(Throwable t) {
              if (done) {
                  RxJavaCommonPlugins.onError(t);
                  return;
              }
              done = true;
              actual.onError(t);
           }
  
          @Override
          public void onComplete() {
              if (done) {
                  return;
              }
              done = true;
              T v = value;
              if (v != null) {
  //                value = null;
                  actual.onSuccess(v);
              } else {
                  actual.onComplete();
              }
          }
  
  
      }
  }
  